Anti-bacterial chemical process



3,282,777 ANTI-BACTERIAL CHEMICAL PROCESS John J. Ceriotti, St. Clair Shores, Mich, assignor to Andrew Peru, Dearborn, Mich.

No Drawing. Filed Feb. 6, 1962, Ser. No. 171,344 5 Claims. (Cl. 16743) The present invention broadly pertains to a novel bactericide composition and mechanism for controlling microbial contamination and degradation, and more particularly to a self-perpetuating bactericide composition and mechanism operative in an aqueous medium to prevent microbial growth or to eliminate any microbial growth in a variety of aqueous organic emulsions and suspensions susceptible to microbial attack.

A large number of different aqueous organic emulsions and suspensions are extensively employed in industry for a variety of different purposes which are susceptible to microbial attack resulting in a progressive degradation thereof necessitating a premature and costly discarding of the materials thus contaminated. The progressive microbial degradation of such materials results in a progressive breakdown of the emulsion or suspension rendering it less effective which in many instances also creates a hygienic hazard to operating personnel exposed to the contaminated materials. One such industrial aqueous organic emulsion susceptible to microbial attack comprises conventional soluble oil formulations which are employed in metal working and machining operations serving the dual function of a coolant and a cutting lubricant. In this specific instance, contact of contaminated soluble oil emulsions with the hands of the machine operators and material handling personnel results in an industrial hygeniec problem causing skin infections, rashes, and dermatitis. Frequently, the progressive contamination of soluble oil emulsions is also accompanied by the formation of an extremely pungent, rancid odor which is extremely objectionable to operating personnel. The progressive growth of the microbes in a soluble oil emulsion also effects a progressive breakdown of the emulsion rendering it ineffective for its intended purpose.

While the present invention has been found eminently satisfactory for use in connection with the inhibition of microbial contamination of soluble oil emulsions, it is also contemplated within the scope of the present inven tion that the novel bactericide composition and mechanism can be employed in a variety of industrial organic emulsions and suspensions such as latex emulsions, urethane foam emulsions, paste suspensions such as starch paste, wood pulp suspensions, and the like, to prevent microbial growth therein rendering the emulsions or suspensions stable and uncontaminated for extensive periods of time. In each case, the composition and self-perpetuating mechanism comprising the present invention is effective to prevent the growth of microorganisms, such as bacteria, yeast, and fungi or to eliminate such microor anisms in emulsions and suspensions which are already partially contaminated.

A variety of bactericides or disinfecting agents have heretofore been used or proposed for use which have not been entirely satisfactory for one or a number of reasons. Some of these disinfecting agents, for example, are effective to curb the growth of microorganisms for a relatively short period of time after which either an immunity is built up by the microorganisms to the disinfecting agents or new strains are produced which are not susceptible to destruction by the disinfecting agents. In addition, many of such disinfecting agents are extremely toxic and thereby represent a substantial health hazard to personnel handling the disinfecting agent during the preparation of the inhibited suspension or emulsion or during use and contact with the inhibited suspension or emulsion. Because States Patent 0 of the immunity developed by the microorganisms to a particular type of disinfecting agent or bactericide it is frequently necessary to increase the concentration thereof to a level which further aggravates the toxic hazard thereof to personnel coming in contact therewith as well as in handling the material resulting in a greater hazard to personnel and increasing the possibility of chemical burns on the exposed skin.

It is accordingly a principal object of the present invention to provide a novel bactericide and self-perpetuating mechanism which fulfills a heretofore long felt need and which overcomes the disadvantages and hazards associated with bactericides or disinfecting agents of the types heretofore known.

Another object of the present invention is to provide a self-perpetuating bactericide which is substantially nontoxic facilitating handling thereof and substantially eliminating the hazards heretofore associated with inhibited aqueous organic emulsions and suspensions.

Still another object of the present invention is to provide an improved self-perpetuating bactericide which is extremely effective in preventing the growth of detrimental microorganisms and which is not susceptible to progressive ineffectiveness as in the case of presently known bactericides since microorganisms cannot build up an immunity to the bactericide comprising the present invention.

A further object of the present invention is to provide a novel bactericide of a self-perpetuating type for aqueous organic emulsions and suspensions which is operative in a slightly acidic range corresponding to the ideal range of the human skin substantially eliminating any detrimental skin infections of the type which are prevalent as a result of exposure to microbial contaminated aqueous organic emulsions and suspensions of the types heretofore known.

A still further object of the present invention is to provide a bactericide and self-perpetuating mechanism for use in soluble oil emulsions of the types employed in metal working and machining operations which substantially increases the useful life of the cutting fluids while concurrently eliminating the industrial hygienic hazards to personnel coming in contact with such fluids.

Still another object of the present invention is to provide a novel method for preventing the growth of microorganisms in aqueous organic emulsions and suspensions which is self-perpetuating maintaining a continuous effective level of the disinfecting constituents during prolonged periods of stagnancy of the fluids and for generating a higher concentration of the disinfecting constituents during periods of use wherein the fluid is exposed to contamination by microorganisms.

Yet still another object of the present invention is to provide a novel bactericide and self-perpetuating mechanism for preventing the growth of microorganisms in aqueous organic emulsions and suspensions which is highly effective, efficient, nonhazardous, simple to control, and of economical use.

The foregoing and other objects and advantages of the present invention are achieved by introducing water soluble inorganic or organic halogen compounds in the aqueous organic emulsion or suspension in an amount suflicient to produce an available halogen content of up to about 50 parts per million (p.p.m.). The dissolved compounds form halogen ions which in combination with suitable oxidizing and/or reducing agents and heat and the presence of suitable promoters or catalysts, if desired, are oxidized 'and/ or reduced to the elemental state wherein they are effective to attack and destroy any microbial contamination present in the emulsion. The halogens in their elemental form are again reduced and/ or oxidized by reducing or oxidizing agents present in the fluid which is maintained in a controlled condition placing them in an ineffective ionic state from which they are again re-oxidized and/ or reduced to the elemental disinfecting state. The self-perpetuating mechanism or oxidation-reduction reaction of the bactericide is operative by controlling the conditions of the medium in which it takes place to maintain a residuary concentration of elemental halogen from about 1 to about 10 p.p.m. providing thereby a continuous disinfecting characteristic in spite of relatively long periods of stagnancy of the fluid. While a large variety of water soluble halogen containing compounds can be satisfactorily employed to achieve a disinfecting property, it is preferred that iodine compounds, and particularly inorganic iodine compounds be employed in an acid medium preferably ranging from a pH of about 5.5 to about 6.5.

Other objects and advantages of the present invention will become more apparent on a reading of the following description and the typical examples provided for the purposes of further illustration.

While the description and typical examples hereinafter provided of the novel self-perpetuating bactericide comprising the present invention is directed primarily for use in connection with the inhibition of soluble oil formula-' tion employed for metal working operations, it will be appreciated that the basic concepts disclosed are applicable to other aqueous organic emulsions and suspensions susceptible to attack by microorganisms. In the illustrative case of soluble oil emulsions, the bactericide can be conveniently added to a concentrate of the soluble oil emulsion which, on subsequent dilution with water, produces a soluble oil emulsion which is inhibited against attack by microorganisms.

The bactericide comprising the present invention is applicable to soluble oil formulations of the general type employed in industry for use in metal forming operatings including high-speed metal turning and cutting operations. Soluble oil emulsions of this general type basically comprise mineral and vegetable oils and an oil-in-water emulsifying agent. Additional constituents which are optionally employed in soluble oil formulations of the types well known in the art include Various surfactants such as wetting agents, soaps and detergents, saponifiable fatty acids and natural fats, as well as coupling agents, organic solvents, corrosion inhibitors and suitable bactericidal agents. The composition of soluble oil formulations of the general type to which the present invention is applicable is set forth in the following table including a list of the constituents and the conventional range of proportions in which they may be employed.

TYPICAL SOLUBLE OIL FORMULATION Ingredient Usable Range, Non-volatile constituents: percent by weight Vegetable or mineral oil (viscosity T yield total available halogen content of up to about 0 p.p.m.

The pH of the concentrate of the formulation in the foregoing table is preferably controlled between about 5.3 to about 5.8 so as to produce a water diluted soluble oil having a pH preferably ranging from about 5.5 to about 6.5.

It was heretofore believed necessary that soluble oil formulations of the type employed in metal working operations be formulated so that the concentrate thereof as well as the diluted emulsion be on the alkaline side having a pH in excess of 7.0. This was believed necessary in order to curb the growth of microorganisms which is retarded in an alkaline medium. Accordingly, the combination of an alkaline medium and a bactericide of the types heretofore known has been partially effective to retard the growth of microorganisms in soluble oil formulations. At the same time, however, the alkalinity of the soluble oil emulsion in combination with the progressive microbial contamination of the soluble oil has been effective to create a defatting and drying of the skin resulting in skin rashes, dermatitis and other minor skin irritations to personnel exposed to the soluble oil emulsions.

In contrast, soluble oil formulations employing the selfperpetuating bactericide comprising the present invention are preferably formulated on the acid side having a pH of less than 7.0, and preferably having a pH ranging from a about 5.5 to about 6.5. This pH range corresponds substantially to the optimum range of acidity for the human skin. At the same time, this pH range is conducive to the propagation of microbial contamination. However, in view of the extreme effectiveness of the bactericide comprising the present invention, no microbial contamination occurs and the problems of skin rashes, dermatitis, defatting and drying of the skin, and other minor skin irritations are substantially completely eliminated. This feature constitutes still another significant advantage of the present invention and overcomes a long standing industrial hygienic hazard associated with the use of soluble oil formulations.

The self-perpetuating bactericide employed in soluble oil formulations of the type hereinabove set forth in addition to other aqueous organic emulsions and suspensions, comprises a suitable Water soluble halogen compound or mixtures thereof susceptible to an oxidation-reduction reaction while in solution effecting thereby a controlled liberation of elemental halogen molecules and halogen complexes which are exceedingly effective in destroying microorganisms. Such microorganisms are introduced in the emulsions as a result of contact with humans or microbially contaminated objects, through the water introduced in preparing or diluting the emulsion, or from the air.

While a large number of different halogen compounds are available for use including both organic and inorganic compounds of fluorine, chlorine, bromine, and iodine, it has been found that inorganic compounds of iodine provide for simplicity in handling and preparing the inhibited emulsion, are economical and of eflicient use, and do not adversely affect the characteristics of the soluble oil emulsion. The basic requisites of halogen compounds which can be suitably employed are that they be relatively soluble in water so as to provide a concentration of 'available halogen of up to about 50 p.p.m., that they are relatively stable and do not decompose on solution, that they are susceptible to an oxidation-reduction reaction wherein the halogen constituents thereof can be oxidized to the elemental active state in which they are active to destroy any microbial contamination in the emulsion and are thereafter susceptible to further reduction in accordance with the self-perpetuating cycle of the bactericide, and that they preferably are non-toxic in handling while in the dry or concentrated form facilitating the preparation and inhibition of soluble oil emulsion concentrates and diluted soluble oil emulsions derived therefrom.

Soluble organic or inorganic compounds of fluorine, chlorine and bromine are less desirable than iodine compounds because of the higher volatility of the elemental halogens formed during the oxidation-reduction reaction, the instability of such compounds, the relatively high toxicity of such compounds as well as the halogen vapors produced thereby, and the greater degree of corrosivity of the emulsion which constitute an objectionable characteristic when employing such compounds in soluble oil emulsions used in cutting or machining metals susceptible to corrosive attack. Examples of organic halogen compounds containing chlorine, fluorine and bromine, which can be employed but are somewhat undesirable because of the aforementioned detrimental characteristics include acetyl-choline bromide, acetyl-choline chloride, abasin, acetyl fluoride, and the like. Suitable iodine containing organic compounds which can be employed include mecholyl iodide and polyvinylpyrrolidone, and the like. In addition to the foregoing organic iodine compounds, organic iodine compounds of the iodo, iodoso, and iodoxy types can also serve as a source of free iodine for use in the bactericide comprising the present invention. Generally, however, the cost of the foregoing organic iodine compounds is extremely high and the availability of the iodine combined therewith is relatively low per unit Weight of the additive employed which necessitates the use of disproportionately high concentration thereof in an aqueous emulsion which generally is undesirable because large concentrations of extraneous additives to such a soluble oil emulsion is not preferred. Many of the foregoing organic halogen compounds are also relatively expensive in comparison to inorganic halogen compounds and this represents a further disadvantage in the use thereof.

Inorganic halogen compounds are preferably employed, particularly iodine compounds wherein the iodine is in the form of periodates, iodates, and iodides of such metals as sodium, potassium, aluminum, zinc, etc. Inorganic iodine compounds such as sodium iodide (NaI), potassium iodide (KI), sodium iodate (NaIO potassium iodate (K hydrated aluminum iodide AlI -6H O), aluminum iodide anhydrous (A1 and the like, 'have been found to be particularly suitable for use in accordance with the practice of the present invention. Equivalent inorganic compounds of the other halogens, namely, chlorine, bromine and fluorine may also be utilized but are not as desirable because of their higher reactivity, instability, toxicity, and corrosivity. The aforementioned inorganic iodine salts on the other hand are less conducive to promoting any corrosive attack of the metal to which the soluble oil emulsion is applied and moreover are readily soluble in the aqueous emulsion even when at relatively low temperatures.

It is also contemplated within the scope of the present invention that elemental iodine crystals can be employed directly as a source of all or a portion of the disinfecting agent which can be added on a controlled continuing basis to maintain an effective elemental iodine concentration in the aqueous emulsion of up to about 50 p.p.m. and the make-up that portion which is carried off on the workpieces. This can be conveniently achieved by employing a porous bed containing elemental iodine crystals through which water at a controlled temperature and flow rate is passed thereby dissolving a controlled amount of the elemental iodine and which iodine containing water is thereafter added to the soluble oil emulsion. An oxidizing and/or reducing agent is employed to reoxidize or reduce the iodine ions formed as a result of the progressive oxidation or reduction of the elemental iodine molecules. In this way, the self-perpetuating mechanism maintains a controlled level of elemental iodine in the emulsion to effect disinfection thereof.

The operating pH range of an inhibited aqueous organic emulsion or suspension in accordance with the practice of the present invention, and particularly soluble oil formulations can broadly range from about 3.0 on the acid side up to about 9.6 on the alkaline side, and preferably from about 5.5 to about 6.5. The appropriate pH of the emulsion is obtained by the addition of suitable acids such as citric and/ or phosphoric acid or bases such as NaOH and Na PO in addition to suitable buffering agents such as NaH PO and Na HPO for an acid buffered solution for example, to maintain the pH of the concentrate and the pH of the subsequent diluted emulsion Within the desired range. Conventionally, when concentrates are prepared so as to produce a diluted emulsion having a pH range within about 5.5 to about 6.5, the concentrate is prepared so as to have a pH ranging from about 5.2 up to about 5.9 which on subsequent dilution with water will render the desired pH of the diluted emulsion.

In addition to the halogen containing compounds, the acidifying or alkaline agents, bufiering agents, the bactericide further incorporates controlled quantities of an oxidizing agent which is operative to oxidize the reduced halogen ions to the elemental state in which they are effective to attack and kill microorganisms in the emulsion. Oxidizing and reducing agents suitable for this purpose include water soluble oxidants such as potassium permanganate (KMnO C101 C10 1 C10 1 10 I05, 0 CrO Cr O etc. and Water soluble reductants such as N0 1 S D CrO4=, Fe++, etc., which are particularly suitable for use in an acid condition. Metal oxide type oxidants such as Na O BaO etc. are not satisfactory since they yield alkaline compounds (NaOH, B-a(O'H) which upset the buffered acid pH of the soluble oil with a disruption of the proper functioning of the self-perpetuating bactericide mechanism. The foregoing oxidizing and reducing agents on oxidizing an iodide and reducing an iodate, or periodate ion to the elemental iodine state in an acid medium result in the formation of water as a byproduct. On the other hand, the use of alternate oxidizing agents operative in an alkaline medium such as a pH ranging from about 7.0 to about 8.5 such as 10 supported by nickel sulfate (NiSO zinc sulfate (ZnSO HBO +mannitol, Cr (SO Fe(SO etc. as catalysts, results in the formation of a precipitate which usually is detrimental to the preferred functioning of the soluble oil and has a tendency of causing it to be corrosive. For this reason it is preferred to employ an acid medium, and particularly one having apH ranging from about 5.5 to about 6.5 which does not produce insoluble precipitates as a result of the oxidation-reduction reaction and which furthermore is the optimum pH range for the human skin.

A typical reduction-oxidation reaction employing inorganic iodine compounds of potassium iodide and potassium iodate in an amount so as to yield a total iodine content of 50 p.p.m. and employing nickel sulfate as a catalyst in an alkaline medium having a pH ranging from about 7.0 to 8.5 is as follows:

The resultant elemental iodine formed in accordance with the above chemical equation may combine with the potassium iodide to form complexes of elemental iodine (KI(I which are effective to destroy microbial con tamination in the soluble oil emulsion. It will be noted that the nickel hydroxide formed as a result of the reaction forms a precipitate which is undesirable and may interfere with the optimum operation of the inhibited soluble oil formulation.

In contrast, the use of a slightly acidic medium such as a pH ranging from about 5.6 to about 6.4 effects an oxidation of iodine containing ions to the elemental state Without the production of a precipitate but instead With the formation of water rendering the soluble oil emulsion substantially free of undesirable insoluble precipitates. The reaction in an acid medium is illustrated in the following chemical partial equation wherein I acts as the reductant and 10 acts as the oxidant:

The elemental iodine formed by the oxidation of the I and simultaneous reduction of the 10 ions as indicated in the equation may in turn form complexes with iodine ions (KI(I which also are effective to destroy microbial growth.

In either case the elemental iodine formed as a result of the reduction of iodine or other halogen ions is subsequently reduced by compounds such as sulfur dioxide (S or ferrous (Fe++ or sulfide (S=) ions which may take from a period of about 2 to 30 minutes due to the extremely low concentrations of the reactive ions. A residual quantity of elemental iodine continuously remains in the emulsion in spite of periods of stagnancy during which a relatively minor degree of reduction of the elemental halogen occurs whereby the emulsion is continuously maintained in a sterile condition. As a result of this continuous self-perpetuating bactericide mechanism, a residual elemental halogen content ranging from approximately 1 to 5 p.p.m. is maintained in the emulsion to prevent contamination by microorganism.

In accordance with the preferred composition and selfperpetuating mechanism of the bactericide comprising the present invention, inorganic iodide and iodate compounds, such a potassium iodide and potassium iodate are employed which require an acid medium to effect the oxidation-reduction reaction. The greater the acidity and the higher the concentration of the reacting ions, the more rapid is the reaction. The use of iodide and iodate ions is particularly satisfactory since the iodide acts as a reductant for the iodate and the iodate acts as an oxidant for the iodide. Accordingly, both types of ions serve as a source of elemental iodine in accordance with the chemical partial equation as set forth below:

51*(reductant) |IO (oxidant) 6H (acid medium) 3I +3H O By controlling the pH of the medium between about 5.5 to about 6.5, the chemical equilibrium of the reaction is controlled so as to limit the concentration of elemental iodine at room temperature to about p.p.m. When this equilibrium is upset by the application of heat, such as encountered by the contact of the fluid with the cutting tool during a metal cutting operation, additional amounts of 1* are oxidized to I and a corresponding equivalent amount of 10;;- is reduced to I providing effective disinfection of the fluid. When the temperature of the fluid again drops to room temperature, the excess I returns to the ionic I state in accordance with the chemical equilibrium of the reaction. A supplementary oxidizing agent includes in the fluid, such as S O for example, is of a controlled moderate oxidizing potential and requires heat to promote its oxidation characteristics. The supplementary oxidizing agent is of insufficient oxidizing potential to oxidize I0 to the periodate (10 form, but sufliciently strong to oxidize a portion of the iodide to the elemental state. The supplementary oxidizing agent supplements the oxidation of the iodate ion and its activity is further controlled by controlling its concentration in the fluid.

In accordance with the foregoing, the addition of heat is effective to raise the concentration of elemental iodine to about 50 p.p.m. and the subsequent removal of heat by the cooling of the fluid efiects a corresponding reduction in elemental iodine concentration to about 10 p.p.m. The several constituents entering the reaction are prevented from depleting by the periodic addition of make-up solutions to the fluid to also make up for the quantity of fluid carried olf on workpieces. The chemical equilibrium is controlled so that even during periods of prolonged stagnancy, a suflicient concentration of elemental iodine (1 p.p.m. to 10 p.p.m.) is present to prevent microbial contamination of the fluid.

A typical formulation of a soluble oil emulsion incorporating a self-perpetuating bactericide of the type comprising the present invention is described in the following example. It will be appreciated that the example is provided for the purposes of further illustration and is not intended to be limiting of the scope of the present invention as set forth in the subjoined claims.

Example A concentrate for preparing an aqueous organic emulsion of the type suitable for use as a cutting fluid was prepared having a composition as set forth in the following table:

INHIBITED SOLUBLE OIL CONCENTRATE Non-volatiles: Parts of weight Mineral oil 16 Total saponifiables 12 Nonsaponified saponifiables 3.5 Fatty acid (oleic) 3.0 Emulsifiers:

Triton X-* 15.0

Triton QS45* 10.0 Hexylene glycol 0.5 Buffer (NaH PO .Na HPO 1.24 Citric acid 0.9 Supplementary oxidizing agent (Na S O 0.5 Reductant (NaNO 1.66 Halogen compound:

NaI 0.15

NaIO 0.11

Volatiles:

Water 23.0 n-Butyl alcohol 2.44

*Rohm & Haas Company,

The pH of the above concentrate was adjusted to a pH of 5.2 by adding an appropriate quantity of an aqueous solution containing 75% phosphoric acid. The above concentration was diluted with water in the proportion of about 2.5 to about 5 volume percent concentrate which provides a satisfactory soluble oil emulsion for use in machining ferrous and nonferrous alloys. For grinding operations a dilution of the concentrate to yield a soluble oil emulsion containing from about 1.25 to about 2.5

volume percent concentrate has been found satisfactory.

During actual use of the diluted soluble oil emulsions prepared from the concentrate as set forth in the foregoing table quantitative tests of the emulsion during use indicated an elemental iodine concentration of about 8 p.p.m. Use of the foregoing concentrate in the preparation of soluble oil emulsions was also found to render the resulting diluted emulsion substantially completely devoid of any microbial contaminations for extensive periods of time, overcoming the industrial hygienic health hazards encountered with soluble oil emulsions of the types heretofore known. A further significant feature of the diluted soluble oil emulsion is its excellent corrosion inhibition characteristics. Ferrous workpieces subjected to contact with the soluble oil emulsion have been found to remain substantially rust-free for a period in excess of hours during storage in open atmosphere.

While it will be apparent that the preferred embodiments herein illustrated are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What is claimed is:

1. A soluble oil formulation comprising an aqueous emulsion of an oil and water, an acid present in an amount sufiicient to produce an acidity of said formulation ranging from a pH of about 5.5 to about 6.5, a selfperpetuating bactericide comprising iodine ions present in an amount sufficient to provide a total available iodine concentration of from about 1 p.p.m. to about 50 p.p.m.,

and an oxidizing agent present in an amount suflicient for oxidizing and reoxidizing at least a portion of the iodine ions to the elemental state and maintaining a concentration of the elemental iodine molecules in excess of 1 p.p.m. in which they are eifective to attack and destroy microbial contamination.

2. A soluble oil formulation comprising an aqueous emulsion of an oil and Water, and acid present in an amount suflicient to produce an acidity of said formulation ranging from a pH of about 5.5 to about 6.5, a selfperpetuating bactericide comprising iodine ions present in an amount sufficient to provide a total available iodine concentration of from about 1 p.p.m. to about 50 p.p.m., and an oxidizing agent selected from the group consisting of C, C10 C10 10 1 MnO Fe+++, CrO Cr O CeO S O and mixtures thereof present in an amount sufiicient for oxidizing and reoxidizing at least a portion of the iodine ions to the elemental state and maintaining a concentration of the elemental iodine molecules in excess of 1 ppm. in which they are effective to attack and destroy microbial contamination.

3. A soluble oil formulation comprising an aqueous emulsion of an oil and water, an acid selected from the group consisting of citric acid, phosphoric acid, and mixtures thereof present in an amount sufiicient to produce an acidity of said formulation ranging from a pH of about 5.5 to about 6.5, a self-perpetuating bactericide comprising a mixture of water soluble alkali metal iodine and iodate compounds present in an amount sufiicient to provide a total available iodine concentration of from about 1 p.p.rn. to about 50 p.p.m., said iodate compound present in an amount suflicient for oxidizing and reoxidizing at least a portion of the iodide ions to the elemental state and maintaining a concentration of the elemental iodine molecules in excess of 1 p.p.m. in which they are effective to attack and destroy microbial contamination.

4. A soluble oil formulation comprising an aqueous emulsion of an oil and water, an acid present in an amount sufiicient to produce acidity of said formulation ranging from a pH of about 5.5 to about 6.5, a buffering agent for maintaining the pH of said formulation Within a range of from about 5.5 to about 6.5, a self-perpetuating bacten'cide comprising a mixture of potassium iodide and potassium iodate present in an amount sufficient to provide a total available iodine concentration from about 1 p.p.m. to about p.p.m., said potassium iodate present in an amount suificient for oxidizing and reoxidizing at least a portion of the iodide ions to the elemental state and maintaining a concentration of the elemental iodine molecules in excess of 1 ppm. in which they are effective to attack and destroy microbial contamination.

5. The method of disinfecting an aqueous soluble oil formulation comprising the steps of introducing iodine ions therein in an amount sufiicient to provide a total available iodine concentration of from about 1 ppm. to about 50 ppm, acidifying and buffering said formulation to a pH ranging from about 5.5 to about 6.5, oxidizing at least a portion of the iodide ions to the elemental state in which they are effective to attack and destroy any microbial contamination in said formulation, controlling the oxidation so as to provide a continuous concentration of said elemental iodine in an amount ranging from about 1 ppm. to about 50 ppm, and reoxidizing said iodide ions formed as a result of the reduction of the elemental iodine back to the elemental state.

References Cited by the Examiner UNITED STATES PATENTS 2,158,446 5/1939 Werft 167-70 X 2,386,252 10/1945 Mendelsohn 167-70 2,902,405 9/1959 Carroll et al. 16770 2,904,470 9/ 1959 Berliner et al. 167-70 2,918,400 12/1959 Leona-m 16770 X 3,013,973 12/1961 Bennett 252-495 3,039,960 6/1962 Bennett 25249.5

DANIEL E. WYMAN, Primary Examiner.

I. R. SEILER, C. F. DEES, Assistant Examiners. 

5. THE METHOD OF DISINFECTING AN AQUEOUS SOLUBLE OIL FROMULATION COMPRISING THE STEPS OF INTROUDCING IODINE IONS THREIN IN AN AMOUNT SUFFICIENT TO PROVIDE A TOTAL AVAILABLE IODINE CONCENTRATION OF FROM ABOUT 1 P.P.M. TO ABOUT 50 P.P.M., ACIDIFYING AND BUFFERING SSAID FORMULATION TO A PH RANGING FROM ABOUT 5.5 TO ABOUT 6.5, OXIDIZING AT LEAST A PORTION OF THE IODIDE IONS TO THE ELEMENTAL STATE IN WHICH THEY ARE EFFECTIVE TO ATTACK AND DESTROY ANY MICROBIAL CONTAMINATION IN SAID FORMULATION, CONTROLLING THE OXIDATION SO AS TO PROVIDE A CONTINUOUS CONCENTRATION OF SSAID ELEMENTAL IODINE IN AN AMOUNT RANGING FROM ABOUT 1 P.P.M. TO ABOUT 50 P.P.M., AND REOXIDIZING SAID IODIDE IONSS FORMED ASS A RESSULT OF THE REDUCTION OF THE ELEMENTAL IODINE BACK TO THE ELEMENTAL STATE. 